1. Field of the Invention
This invention relates generally to tuning transmission channels and, more specifically, to a method and apparatus for tuning television channels that transmit PSIP (Program and System Information Protocol) Transport Streams and non-PSIP Transport Streams.
2. Related Art
It is known that broadcasters can transmit television programs through a broad-band frequency spectrum of RF (radio frequency). The broad-band frequency spectrum is divided into many sub-band frequency spectrums. A unique number is assigned to identify each of the sub-band frequency spectrums. A sub-band frequency spectrum with a unique number is defined as a physical channel. A physical channel can be used to implement an analog channel, or one or more digital channels. Thus, a particular broadcaster can use one or more physical channels to transmit its television programs.
FIG. 1 shows exemplary channel configurations within a broad-band frequency spectrum 102. As shown in FIG. 1, the broad-band frequency spectrum 102 is divided into 38 physical channels numbered from 2 to 39.
According to PSIP protocol, a virtual channel is the designation, usually a number, used as the single entity that provides access to an analog television program or a set of one or more digital elementary streams. It is called "virtual" because its identification may be defined independently from its physical channel identification. Exemplary configurations of virtual channels are: a digital radio channel (audio only), a typical analog television channel, a typical digital television channel (composed of one audio and one video stream), multi-visual digital channels (composed of one or more data streams). According to PSIP protocol, each virtual channel is associated with a major channel number and a minor channel number.
As shown in FIG. 1, an analog channel 3 links to the physical channel 3, an analog channel 4 links to the physical channel 4, two digital channels 4.1 and 4.2 link to the physical channel 38, and two digital channels 6.1 and 6.2 link to physical channel 39. The physical channels as shown in FIG. 1 are configured into three groups. In group 1, the physical channel 3 is licensed to a first broadcast organization. In group 2, the physical channel channels 4 and 38 are licensed to a second broadcast organization. In group 3, the physical channel 39 is licensed to a third broadcast organization.
At the user side, number 3 designates an analog channel for the first broadcast organization. Number 4 designates a major channel (4) for the second broadcast organization, and the numbers 1 and 2 designate two minor channels (4.1 and 4.2), respectively, for the second broadcast organization. The number 6 designates a major channel (6) for the third broadcast organization, and the numbers 1 and 2 designate the two minor channels (6.1 and 6.2) for the third broadcast organization.
As shown in FIG. 1, if a channel group includes analog and digital channels, number 0 is used in minor channel number position to designate the analog channel. For example, analog channel 4 is designated as 4.0. However, if a channel group includes only an analog channel, number 0 will not be used to designate any channel. For example, analog channel 3 is designated as 3, not 3.0.
FIG. 2 shows a packet 200 in a PSIP Transport Stream (TS) according to the ATSC (Advanced Television System Committee) standard. There are two formats of data in the PSIP packet 200. One is called PES (Packetized Elementary Stream) format. Video, audio, and data are packed in PES format. The other is called Section format defined by ISO/IEC 13818-1 standard. PAT (Program Association Table), PMT (Program Mat Table), and PSIP sections are packed in Section format.
A PAT section contains a list of PIDs (Packet Identifiers) to a set of PMTs. A PMT section includes PIDs to audio, video, and data PESes that form a particular television program. A Transport Stream contains many packets. Each of the packets has a PID in its header, and this PID is used for collecting and recovering PES and Section data.
The PSIP section contains a plurality of tables, including STT (System Time Table), MGT (Master Guide Table), VCT (Virtual Channel Table), RRT (Rating Region Table), EIT (Event Information Table), and ETT (Extended Text Table). These tables are defined by Program and System Information Protocol published by the Advanced Television Systems Committee on Dec. 23, 1997. Specifically, the PSIP section contains the information regarding program title, a major channel number, and minor channel number(s). The PSIP protocol is hereby incorporated into the present application by reference.
FIG. 3 shows a packet 300 in a non-PSIP Transport Stream according to ISO/IEC 1318-1 Standard (ISO stands for International Standard Organization, and IEC for International Electrotechnical Commission). As shown in FIG. 3, the packet 300 has a similar structure as that of the packet 200, except that the packet 200 does not have a PSIP section. The ISO/lEC 1318-1 Standard is hereby incorporated into the present application by reference.
As described above, the PSIP section in the PSIP packet 200 contains a major channel number and minor channel number(s). Thus, upon receiving a PSIP Transport Stream, a television set can display a major channel number and a minor channel number to identify the channel selected, based on the information in the PSIP section. However, a non-PSIP Transport Stream does not contain a major channel number and minor channel number(s), because it does not have any PSIP sections.
There is, therefore, a need to provide a method and apparatus for tuning transmission channels that transmits either PSIP Transport Streams or non-PSIP Transport Streams.
There is another need to provide a method and apparatus for tuning transmission channels that transmit either PSIP Transport Streams or non-PSIP Transport Streams without using different user hardware and software interfaces.
The present invention provides the methods and apparatuses to meet these two needs.